Specify INFO log severity for -XX:DumpGCPerformanceOnShutdown

The art script only has severity set to warning, this was causing
the GC timings to not get output.

Bug: 70630582
Test: art -Xmx512m -XX:DumpGCPerformanceOnShutdown .. some benchmark

Change-Id: I03e4e09836f0bd73fbbff3640b4db8617cc63c95
diff --git a/runtime/runtime.cc b/runtime/runtime.cc
index 7239ad3..1cdeb7c 100644
--- a/runtime/runtime.cc
+++ b/runtime/runtime.cc
@@ -297,6 +297,7 @@
   }
 
   if (dump_gc_performance_on_shutdown_) {
+    ScopedLogSeverity sls(LogSeverity::INFO);
     // This can't be called from the Heap destructor below because it
     // could call RosAlloc::InspectAll() which needs the thread_list
     // to be still alive.